A. Field of the Invention
This invention generally relates to personal propulsion devices that are worn on the back of a user or attachable to a moveable object, such as a bicycle, canoe, skateboard or other human-powered vehicle, ridden by the user to propel the user and the object. More specifically, this invention relates to such devices that provide for hands-free operation and control of the device and are configured to accept adjustments for versatility. Even more specifically, this invention relates to various improvements to the configuration of such devices that improve the usefulness and functionality of the device.
B. Prior Art
User-worn propelling devices to propel a person riding on or in a moveable object, such as a bicycle, skateboard, canoe, pair of skates and the like, are well known in the prior art. For instance, the propelling device of Morrill, U.S. Pat. No. 2,456,440, discloses a thrust device that is supported by one arm only. Unfortunately, the user is imbalanced by the offset weight and the center of thrust is in line with the one supporting arm of the user and, therefore, misaligned or offset from the center of resistance of the user's skates, as shown in FIG. 3 of that patent. Torque about the user's vertical axis makes straight line travel and maneuverability difficult. Support of the device by one arm will rapidly become fatiguing to that arm and long duration travel will be uncomfortable or intolerable. The support bar along the side of the user, the gas tank and the throttle appendage in front of the user become a hazard in the event of a fall. The engine is located behind the propeller, thereby increasing the distance from the support and, therefore, increasing the cantilevered weight to the user's arm. Riding a modern bicycle with only one hand is dangerous as two brake handles are provided for safety in traffic. Sitting in and operating a wheelchair requires both hands for steering. The engine would interfere with sitting in the wheelchair. In a canoe or kayak, the engine would interfere with both hands and arms being required for the paddles. An engine speed of 18,000 to 20,000 rpm is dangerous as propellers can and do shatter, which may cause serious injuries to the user and bystanders. Six pounds of thrust is low and insufficient for overcoming inclines and soft snow with heavier users, and slow in watercraft against even a light wind.
The propulsion support unit of U.S. Pat. No. 4,189,019 to Zech, discloses a complex system of levers, springs, turntable and bars on both sides of the users' body. Both hands and arms are required for controls. The unit described with a 25-30 lb. motor, plus frame and support unit, would weigh approximately 40 lbs with the propeller and protection shroud. The frame top terminates in rigid tube ends which during a fall may on contact with the back or sides of the head and neck cause injury to the user. The control bars at the sides of the user present a further injury hazard in the event of a fall. The unit would be impossible to operate on a bicycle, and the position on the user's body would interfere with a canoe, kayak and wheelchair. On snow skis the requirement of both hands and both arms renders the user unable to grip and maneuver the pair of ski poles essential for balance, turning and accelerating over rough terrain. The many parts, heavy weight, high cost of manufacturing, hazardous in a fall, and both hands and arms occupied, make this invention less attractive as an alternative form of transportation.
Zech further discloses a propeller shroud, as shown in FIG. 7. A sufficient body of research has proven the thrust is reduced substantially by shrouding, compared with an open propeller, without including an “inlet lip” of 15% diameter of the shroud (see Modern Propeller and Duct Design by Martin Hollman, 1993, pg 101—incorporated herein by reference). The current invention includes a bumper/flotation device that cooperates with airflow at the inlet end of the containment ring.
The propulsion means set forth in U.S. Pat. No. 5,222,569 to Martel, discloses a device that imparts thrust “solely to the rear of the pelvic area.” The propulsion device is supported by a pendulum shoulder harness on the user and must be controlled by both hands on a pair of grips and pivoting handles along both sides of the user. These side handles are an injury hazard in a fall. The device is hanging free on the pendulum harness except for the users hands on the two handle grips, so in the event of a fall when the users hands release the handles to break the fall, the unit can swing around the neck or impact the users head and neck causing injury. The foot starting cable may become entangled around the user causing further injury. The device is located below the axis centered on the pelvic region and the user may not sit in a canoe, kayak, wheelchair or bicycle. Further more the users hands would be unavailable to grasp the required maneuvering implements such as paddles, brakes, handle bars, wheels of the wheelchair etc. If the user released the handles to grasp implements the unit would swing out of control causing an impact hazard. The propulsion device does nothing to improve open propeller inefficiencies (see Modern Propeller and Duct Design by Hollman, 1993, pg. 95 and 97—incorporated herein by reference).
The current invention will overcome the above referenced hand and arm requirements. It will allow hands free operation and control of a simple light weight, efficient, economical, device that is adjustable up and down the user's back. The current invention eliminates the need for any side bar for control. This will allow co-operative use with any of the well known transportation or recreational human powered vehicles (HPVs) such as bicycles, kick scooters, wheelchairs, canoes, kayaks, small sail craft, skateboards, all ice and roller skates, snow skis, and etc. In addition, the current invention anticipates use proximate to crowds of people and, therefore, has many safety and convenience improvements.
The light aircraft with inflatable parachute wing propelled by a ducted propeller of U.S. Pat. No. 5,620,153 to Ginsberg, teaches that the efficiency of an aircraft propeller is reduced at low speeds and can be improved by the addition of a duct, comprising support vanes to counter act the torque of the engine, and a propeller or fan centered and mounted rotationally within. The addition of the duct improves safety, reduces noise and improves thrust to power ration. Further study teaches that a ducted fan or shrouded propeller comprises an inlet lip attached and tangent to the duct with a special fan, turbine, or propeller of greater surface area than standard open aircraft propellers of the same diameter. It is known in the art that a very close tolerance between the propeller and the interior surface of the duct, 0.015 inch maximum up to an 18 inch diameter propeller is required. This close tolerance requires stiffened duct and vane arrangement and the cost of the composites and manufacturing of them, to stiffen the unit and retain the light weight features required in aircraft is prohibitive for a personal propulsion device. The rpm is also increased in a ducted fan and results in an unacceptable blade failure risk proximate to crowd and children on bicycle paths, sidewalks, and boardwalks for ground transportation.
The current invention overcomes the dangers of the ducted fan and the prohibitive cost of the rigidity required and the lack of availability of ducted fan parts in the required sizes. The inlet lip is of a complex increasing radius design which also increases design and manufacturing costs (see Modern Propeller and Duct Design by Hollman, 1993, pg 101 and 102—incorporated herein by reference).
The current invention improves the efficiency of the open propeller and improves the personal propulsion device safety using commonly available materials of very low cost and weight. The manufacturing processes required are simple and inexpensive. The propellers required are commonly available for large model aircraft in wood, plastic, fiber reinforced nylon, and other materials. The diameters and pitches are diverse and can be adapted for use in the current invention for any rpm, size user, or horsepower required in a two, three or multiple blade configuration.
The recoil rope type manual starters that are standard in the industry have been improved to be operable from the user position. Tezuka et. al, U.S. Pat. No. 6,776,133, discloses a starter extension that is pulled along side the operator in the standard working position. None of the prior art machines adjust slidably up high on the users back and down low on the users back. This wide variation in propulsion device positions on the user, would dispose the starter handle in the region of the arm pit at its high adjustment. This position removes the strength and leverage advantage of the operators arm, against the load, due to the inconvenient position. The various positions on the users back facilitated by the current invention, would place the fixed end of the flexible tube and its fixing bracket, as shown in FIG. 3, in the path of the swinging arm or elbow of a canoe paddler or snow skier. The rigorous anticipated and intended uses of this current invention require free motion and unobstructed use of arms and elbows through their full range of motion, without chance of impact or contact with any part of the propulsion device. My current invention will over come the limitations and injury hazards of the prior art recoil starters.
The prior art of personal propulsion means attached directly to the user has resulted in heavy, slow and generally inefficient devices. One or both of the hands and arms are continuously required for control of these devices. There are handles and appendages that create a safety and/or injury hazard to the user in the event of a fall. The devices lack sufficient adjustments in position on user, and thrust angle to provide wide versatility in cooperation with the many HPVs available today. As a result, presently there are no personal propulsion devices that are widely available on the market, therefore, the public has benefitted little from the prior art devices.
As freeway, street, and parking lot crowding increase, the demand and cost of fossil fuels are at a record high world wide. Pollution from auto emissions is an increasing concern of the public and the global warming awareness is on the increase. The dependency of the United States on foreign oil and the consumption of world wide petroleum reserves will create new record high prices. Emerging countries' fuel demand in conjunction with the aforementioned pressures, point to ever increasing prices and ever tightening supplies.
A need exists for a compact, extremely low fuel consumption, user friendly, hands free operation, light weight, low emissions, unlimited range (with occasional refueling at any gas station) alternative transportation device. This need for alternative transportation is recognized widely as bicycle paths and designated bicycle lanes on streets and roads are being built at great cost and prompted aggressively. This is occurring in large cities and small towns alike, as the negative impact of too many automobiles is pervasive. The popularity of HPVs is at an all time high. The range of HPVs has always been limited by the endurance of the user and thereby eliminating much of the public from benefitting from such devices.
The massive competition in the lawn and garden equipment market has resulted in rapid and major improvements to the motors. The resulting improvements directly benefit the present invention. The major improvements are reliability, manufacturer's product up to 2000 hrs of trouble free use. Emissions reductions; the public and community awareness of small engine pollution (especially two-strokes where oil is pre-mixed with gas) and in co-operation with state air resources agencies, have ever tightened standards of compliance among small engine manufacturers. User friendly features are now major selling points such as lighter weight and high power. Currently a 2.2 hp totally self contained motor weighs only nine pounds. Other features include a fuel primer bulb for first pull and easy starting, all position running, quieter mufflers, regular gas required with greater fuel economy and less vibration to the user.
The current invention benefits from the motor configuration of the increasingly popular string trimmer. There are many manufacturers to select from. There are many power options and option packages to select from. A size and weight range of the present invention can be offered to the public to accommodate various sizes of users. The operator of the string trimmer benefits from the vibration isolation bushing between the engine and drive shaft housing and the current invention will benefit also.
For the rest of this document the term string trimmer motor is implied to comprise the standard, widely available string trimmer motor which is totally self contained. It includes a centrifugal clutch so at an idle condition the load is at rest. It includes a leak proof all position fuel tank. It includes a recoil rope starter. It includes a vibration isolation bushing between the motor and the drive shaft housing tube. It includes a muffler and or catalytic converter and or spark arrester as local regulations require. It includes a carburetor having a fuel primer squeeze bulb, a convenient choke, a throttle, and an air filter. It may be of either the two stroke, more noisy and requiring premixed oil in the gas, but is lighter, or the four stroke, quieter, less exhaust emissions, uses regular gas but is heavier per horse power. These motors have smooth exterior cowlings and are air cooled. Noise awareness is on the increase worldwide.
Excessive noise associated with operating equipment, machinery, vehicles and other devices is generally considered to be noise pollution in the United States is increasingly regulated by many local, state and federal agencies. A personal propulsion device utilizing a propeller generally has the propeller positioned close to the user's ears and often in close proximity to bystanders. As such, propeller noise is of particular importance to such a device and its users and the public at large. A fixed-pitch propeller is preferred for this application due to its low cost, low weight, and low maintenance required. Fixed-pitch propellers will be considered for this invention while acknowledging that a light weight variable pitch propeller may be incorporated in combination with this invention.
Testing of propeller thrust versus noise levels indicates that significant reductions in noise by modern reduced noise propeller designs results in a corresponding or greater percentage loss in propulsive efficiency (in the twelve inch diameter to twenty inch diameter size range tested). It is broadly understood that the region nearest the propeller tips, having the greatest velocity, generate the greatest noise. The need exists for a light weight propeller/shroud system that can be controlled to minimize noise while still producing thrust, even at a reduced thrust level and power to thrust ratio.
Materials selection for a device with widely varied mechanical properties generally requires fastening together a number of different materials, each for a specific quality of rigidity, one for flexibility, one for colorability, one for weather proofing or water proofing and another for user comfort. The age-old method for building such devices generally requires many patterns, parts and fasteners, and the strength is generally limited by the weakest material in the system or material separation at the points where fasteners penetrate the material. The need exists for a material that can have widely varied mechanical properties imparted to various areas, ridged and strong in some areas and flexible in others and elasticity/stretchability in yet other areas, all from a single piece of material.